Apparatuses for measuring heat flows through solid objects are previously known, for instance from DE 27 24 846, JP0533285 and CN 2476020.
JP0533285 refers to an equipment and a method for measuring the heat flow through materials. According to the known solution, a first sensor is arranged onto the material which is investigated and another onto a separate insulation layer; the actual measuring principle and related electronics are based on the Wheatstone bridge.
CN 2476020 describes an equipment for testing of the coefficient of heat transfer. The equipment comprises a box which can be placed onto the inside surface of a house wall, in order to measure the heat flow of the wall. The box is filled with air, and a thermosensor and a thermal resistance are placed inside the box. The power consumption is approximately 130-150 W. The box is designed for measuring walls having a U-value of 0.5 W/m2 K. As it is a question of a box having large dimensions of almost half of one or one square meter, the equipment is not suitable for measuring heat flows, for instance, in a corner or over thermal bridges with a limited physical size in building structures. Moreover, it should be noted that the thermal resistance of the interface between air/wall surface is affected by the box itself, because the air in the box does not circulate in the same way as at a free wall surface.